Add xgrammar

[maresb]

Checklist

• Title of this PR is meaningful: e.g. "Adding my_nifty_package", not "updated meta.yaml".
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[github-actions]

Hi! This is the staged-recipes linter and your PR looks excellent! 🚀

[conda-forge-admin]

Hi! This is the friendly automated conda-forge-linting service.

I just wanted to let you know that I linted all conda-recipes in your PR (recipes/xgrammar/recipe.yaml) and found it was in an excellent condition.

[maresb]

The build is complicated by these submodules: https://github.com/mlc-ai/xgrammar/tree/main/3rdparty

Also, I'm not sure why the CI started skipping the builds.

This is likely to go stale, so others are encouraged to continue the effort.

[zbowling]

@maresb oh hello again. #29064

[maresb]

Superseded by #29064